The invention relates to a method of controlling the travel speed of a unit in a machine for processing printing materials, which includes monitoring the travel speed by a first measuring device.
The published European Patent Document EP 0 799 783 A2 describes a control for a sheet-pile lifting drive, which includes a monitoring device for receiving a signal from an evaluation unit via a line precisely at an instant of time when the travelling speed of a pile-carrying plate exceeds a maximum value defined as a function of position. In this case, a drive motor is stopped by the monitoring device. A drawback of the aforedescribed control is that if the monitoring device fails, consequential damage can occur.
The invention further relates to a device for controlling the travel speed of a unit in a machine for processing printing materials, having a motor for driving the unit, which is activatable as a function of instantaneous travel positions of the unit, and having a rotary encoder for registering the instantaneous travel positions.
A device of this general type is; for example, the control described in the aforementioned published European patent document, which has a rotary encoder constructed as an absolute rotary encoder. A drive motor driving the pile-carrying plate is connected to the rotary encoder via a reduction transmission or gearbox so that the entire travel path of the pile-carrying plate does not quite produce one revolution of a rotor of the rotary encoder.
It is accordingly an object of the invention to provide a method and a device for controlling the travel speed of a unit in a machine for processing printing materials wherein the machine has a high operational reliability.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of controlling the travel speed of a unit in a machine for processing printing materials, including monitoring the travel speed by a first measuring device, which comprises additionally monitoring the travel speed by a second measuring device belonging to the machine.
In accordance with another mode, the method of the invention includes, during fault-free operation of the machine, simultaneously monitoring the travel speed of the unit by the first measuring device and by the second measuring device, which acts independently of the first measuring device.
In accordance with a further mode, the method of the invention includes detecting by the second measuring device an excessive speed of travel of the unit, resulting from a failure of the first measuring device, and, by the second measuring device, switching over a motor, which drives the unit, to a reduced rotational speed or to stop it.
In accordance with an added mode, the method of the invention includes monitoring the travel speed by the first measuring device over the entire travel distance of the unit, which lies between two opposite end positions, and monitoring the travel speed by the second measuring device only in a critical section of the travel distance.
In accordance with an additional mode, the method of the invention includes having the unit move through the critical travel section shortly before moving a gear wheel fixed to the unit into engagement with a further gear wheel.
In accordance with a second aspect of the invention, there is provided a device for controlling the travel speed of a unit in a machine for processing printing materials, having a motor for driving the unit, the motor being activatable as a function of instantaneous travel positions of the unit, comprising a rotary encoder for registering the instantaneous travel positions, the rotary encoder being constructed as a relative rotary encoder.
In accordance with another feature of the invention, the rotary encoder has a sensor assigned thereto for detecting an end position of the unit, the end position serving as a reference value for automatically calculating the instantaneous travel positions.
In accordance with a further feature of the invention, the rotary encoder has a rotor to which the unit has a drive connection via a gear transmission so that, as the unit moves from one end position to an opposite end position of the unit, the rotor executes a plurality of complete revolutions.
In accordance with an added feature of the invention, the rotary encoder has a control link with a computer for adding up the revolutions, the computer having a control link with the motor.
In accordance with an additional feature of the invention, the rotary encoder is a two-channel tachogenerator.
In accordance with yet another feature of the invention, the control device includes a first measuring device for monitoring the travel speed of the unit, comprising a first monitoring device formed by the rotary encoder, and a first computer linked to the first monitoring device, and a second measuring device for monitoring the travel speed of the unit, comprising a second monitoring device formed by a switch operatable by a cam, and a second computer linked to the second monitoring device.
In accordance with yet a further feature of the invention, the unit is a varnishing device in one of a printing and a varnishing unit, respectively, of a rotary printing machine.
In accordance with yet an added feature of the invention, the unit is a pile-lifting unit in one of a sheet feeder and a delivery, respectively, of a rotary printing machine.
In accordance with a concomitant aspect of the invention, there is provided a machine for processing printing materials, in particular a rotary printing machine, having a device for controlling the travel speed of a unit in the machine, including a motor for driving the unit, the motor being activatable as a function of instantaneous travel positions of the unit, comprising a rotary encoder for registering the instantaneous travel positions, the rotary encoder being constructed as a relative rotary encoder.
Thus, the method according to the invention is distinguished by the fact that the travel speed is additionally monitored by a second monitoring device belonging to the machine.
During fault-free operation of the machine, at least from time to time parallel monitoring of the travel speed is carried out by both measuring devices, so that even in the event of failure of the first measuring device, damage resulting therefrom such as pinching or squeezing or other injuries to the operator of the machine, and the breaking out of teeth of a couplable gear transmission belonging to the machine are reliably avoided.
The control device according to the invention is distinguished by the fact that the rotary encoder is constructed as a relative rotary encoder.
On a region or range of 360xc2x0 of a rotor of the relative rotary decoder, only a specific portion or length of the entire travel path of the unit, i.e., not the entire length of the travel path, is projected.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for controlling the travel speed of a unit in a machine for processing printing materials, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.